The present invention pertains to the technical field of methods and apparatus to be used for presentation of calling subscriber number identification in mobile networks when calls pass through other intermediate networks, and particularly to the technical field of methods and apparatus aimed to avoid that said calling subscriber number identification is lost due to the lack of means in said intermediate networks for transferring such identification data.
The present invention provides the necessary steps and means to transfer said calling subscriber number identification data through a network enabling such a transmission, like the mobile network, and by protocol means separate from the call.
Most of the currently existing mobile networks make use of the Integrated Services Digital Network (hereinafter referred to as ISDN) and its corresponding ISDN User Part protocol (hereinafter abbreviated as ISUP) to switch and transfer calls, both internally within the mobile network and externally to or from other networks. In this respect, particular ISDN numbers identify individual subscribers of an ISDN-based network. Moreover, some mobile networks like the Global System Mobile network (generally known and hereinafter referred to as GSM) and the Universal Mobile Telecommunications System (generally known and hereinafter referred to as UMTS) identify their own subscribers by a Mobile Subscriber ISDN Number (generally known and hereinafter referred to as MSISDN).
Nowadays, UMTS is considered the third generation (hereinafter abbreviated as 3G) of mobile systems to which the current second generation (hereinafter abbreviated as 2G) of mobile systems is converging. An appropriate example of a 2G mobile system is the above mentioned GSM. Still another example of 2G mobile systems is the Pan-American mobile system based on the Interim Standard number 41 (generally known and hereinafter referred to as IS-41). Both GSM and IS-41 based networks are evolving towards the UMTS network. Nevertheless, these and other mobile systems of different generations should still co-exist and communicate each other. Still another 3G mobile network is the Pan-American system based on Code Division Multiple Access (generally known and hereinafter referred to as CDMA2000) to which 2G Pan-American mobile systems are also evolving.
In a similar manner as UMTS and CDMA2000 inherit most of the features and services already existing in the 2G mobile systems, the latter had inherited services from ISDN. For instance, ISDN supports several Supplementary Services related to the presentation of ISDN numbers, which were already included in mobile systems like GSM or IS-41 based systems, and which will still be supported by UMTS and CDMA2000, and other systems. Examples of these ISDN supplementary Services supported also in such mobile networks are commented below:                i) Calling Line Identification Presentation (hereinafter referred to as CLIP) is a supplementary service that provides the ability of indicating the ISDN number of the calling line, namely the calling subscriber, with possible additional sub-address information to the called party. It is also named Calling Number Identification Presentation (CNIP) under some standards.        ii) Calling Line Identification Restriction (hereinafter referred to as CLIR) is a supplementary service that precludes the presentation of the calling line identification if the calling user has an arrangement to inhibit such a presentation of his or her number to the called party.        iii) Connected Line Identification Presentation (hereinafter referred to as COLP) is a supplementary service that provides the ability to the calling party to present the connected party's ISDN number, namely the called or connected subscriber.        iv) Connected Line Identification Restriction (hereinafter referred to as COLR) is a supplementary service offered to the called party to restrict the presentation of the connected line, namely the called subscriber or another forwarded-to number, to the calling party.        
When invoking the CLIP supplementary service, the information to be transferred by ISUP to the destination end side is provided by the originating end user in the SETUP message and sent as part of the basic call procedures. In the case when the calling user provides no information, the network shall provide the default number associated with the user access in the originating local exchange. This calling number is transferred through the ISUP network to the destination end side and provided to the called user at call set-up.
In addition to this call-establishment related signalling through ISUP, mobile specific signalling is exchanged between different mobile network entities to appropriately route the call to or from the area where the mobile subscriber is currently roaming. In this respect, the standard signalling messages and message parameters involved in said specific mobile signalling are described in the Mobile Application Part (hereinafter referred to as MAP) specification 29.002 v3.4.0 issued by the 3GPP Technical Specification Group Core Network (hereinafter said specification is referred to as 3GPP TS 29.002).